Yes, with no issues. Blackhorn 209, as you can tell from its name, is intended for use primarily with 209 shotshell primers. That is no different from Hodgdon Triple Se7en pellets, which Hodgdon has always said are for use with 209 primers only.

A generalized statement like that naturally cannot take into account all breechplug designs, including breechplug length and flash hole diameters. The Remington Ultimate has a large, .041 inch flash hole diameter and is a fairly short breechplug, certainly short compared to the interrupted thread, allegedly hand removable types. The sealed breech design, the large rifle primers, the short breechplug and the large flash hole all combine to make the Remington Ultimate ideal for Blackhorn 209, or Triple Se7en pellets.

Where can I get one?

Any gun shop can stock them or order them. Both Cabela's and Gander Mountain have picked them up, but quantities are limited. If he doesn't have one in stock, your local Remington dealer can order one for you.

Is the Remington a form 4473 firearm?

Yes, the bolt has locking lugs and that means you need to get one through a FFL holder. Not much of an issue, as the FBI reported that it performed an astounding 21,093,273 background checks last year alone. The switch barrel genre of guns (Encore, Contender, Knight KP1) are all form 4473 arms, as are shotguns that have been used as muzzleloaders (Mossberg 500).

The original Savage 10ML had locking lugs, yet the ATF ruled that it was a non-form 4473 arm, initially. Then, for no apparent reason, they changed their minds and the original Savage 10ML remains a form 4473 arm, while the 10ML-II is not. This is a remarkably stupid decision by the ATF, as muzzleloaders and large, heavy single shot rifles aren't used to commit crimes; even Captain Obvious knows that.

Yes, they shoot quite well in my gun. The bullet essentially is the excellent Barnes 250 grain Spit-fire T-EZ flat base, but sized to .4485 inch. The green sabot is a proprietary Remington sabot, developed by MMP and Remington specifically for the Remington 700 Ultimate. It has a 25-30% higher tensile strength than any other sabot.

What is the bore diameter?

The barrels of the Remington Ultimate run about .5015 inch.

What velocity can be produced with four T7 50 grain pellets and 250 grain Remington Accu-tip bullets?

How does this Remington Ultimate compare to the $3000 - $4000 Michigan Ultimate rifle?

The Remington 700 Ultimate is a better gun, as it fixes the numerous design flaws of the Michigan Ultimate that are breechplug and primed brass related. The Michigan Ultimate uses large rifle primers in a large pistol parent case (.45 Winchester Magnum).

Remington recommends repriming their brass 5 times, although they have gone up to 12 times. The Remington brass, based on the .308 case, has a machined chamfer, for a better seal than just attempting to rely on a stamped flash hole, which was found sometimes not to seal in Remington testing. With the chamfer, the primed brass is seated correctly every time, not all over the map. Also, the breechplug itself seals better.

The Remington breechplug is made from 416 stainless hardened to 58 HRC max, a harder and stronger breechplug than the comparatively soft 300 series Michigan Ultimate plug. The Remington breechplug is not only harder and stronger, it does not have the erosion problems associated with four pellet Triple Se7en loads of the Michigan Ultimate plug, according to Remington testing. To summarize, the entire breeching system in the Model 700 Ultimate has been redesigned and the end result is a big, tangible improvement.

What is the best load in my individual Remington Ultimate?

If there were such a thing, that is what we would all be using. As time goes by, Remington 700 Ultimate owners will naturally come up with their favorite loads, tailored to their individual rifles and their own personal preferences. Based on testing in my rifle, these are all MOA combinations:

Recoil, according to my shoulder, is getting distracting with 143 grains volume BH209 with 300 grain saboted projectiles, but is still manageable with 250 grain saboted bullets. Your shoulder may tell you differently.

That's going to be personal preference. The synthetic stock is essentially the Bell and Carlson Medalist M40 Varmint/Tactical Rifle Stock Remington 700 BDL Short Action with Aluminum Bedding Block System Varmint Barrel Channel that sells, stock only without hardware, from Midway USA for $290.

According to Remington, there is no discernible accuracy difference between the models. My preference is the laminated version, which sells for a bit less and includes iron sights. I like the cheek piece and it is, by far, the better looking stock.

I'm personally all worn out on the pervasive break-action hinge-pin hammer gun version of ugly. There seems to have been some sort of unofficial competition in the muzzleloading market as to who can sell the ugliest front-loader with the nastiest tupperware stock, the noisiest cocking and the slowest lock-time.

To me, the laminated Remington Ultimate Laminated is, by far, the best-looking production muzzleloader now on the market. There is no performance-based reason not to go laminate and it sure is easy on the eyes, so that's my preference.

What Accessories Do I Need?

In the case of the laminated model, everything you need to shoot is in the box except propellant. In my case, after removal of the rear peep sight, I installed a Warne M676M one piece rail. I used Warne Maxima medium height quick release 30mm rings to mount a Hawke Endurance 30 2.5-10x50mm scope with the illuminated LR Dot ballistic reticle. I also added a Gunn Innovations ramrod, which has a Spinjag attached.